Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. Pacemakers and Implantable Cardiac Defibrillators (ICDs) have proven highly effective in the treatment of a number of cardiac conditions (e.g., arrhythmias). Spinal Cord Stimulation (SCS) systems have long been accepted as a therapeutic modality for the treatment of chronic pain syndromes, and the application of tissue stimulation has begun to expand to additional applications such as angina pectoralis and incontinence. Deep Brain Stimulation (DBS) has also been applied therapeutically for well over a decade for the treatment of refractory chronic pain syndromes, and DBS has also recently been applied in additional areas such as movement disorders and epilepsy. Further, Functional Electrical Stimulation (FES) systems such as the Freehand system by NeuroControl (Cleveland, Ohio) have been applied to restore some functionality to paralyzed extremities in spinal cord injury patients. Furthermore, in recent investigations Peripheral Nerve Stimulation (PNS) systems have demonstrated efficacy in the treatment of chronic pain syndromes and incontinence, and a number of additional applications are currently under investigation. Occipital Nerve Stimulation (ONS), in which leads are implanted in the tissue over the occipital nerves, has shown promise as a treatment for various headaches, including migraine headaches, cluster headaches, and cervicogenic headaches.
These implantable neurostimulation systems typically include one or more electrode carrying stimulation leads, which are implanted at the desired stimulation site, and an implantable pulse generator (IPG) implanted remotely from the stimulation site, but coupled either directly to the stimulation lead(s) or indirectly to the stimulation lead(s) via a lead extension. Thus, electrical pulses can be delivered from the IPG to the stimulation leads to stimulate the tissue and provide the desired efficacious therapy to the patient.
The neurostimulation system may further comprise a handheld external control device in the form of a remote control (RC) to remotely instruct the IPG to generate electrical stimulation pulses in accordance with selected stimulation parameters. A typical stimulation parameter set may include the electrodes that are acting as anodes or cathodes, as well as the amplitude, duration, and rate of the stimulation pulses. The RC may, itself, be programmed by a clinician, for example, by using a clinician's programmer (CP), which typically includes a general purpose computer, such as a laptop, with a programming software package installed thereon. Typically, the RC can only control the IPG in a limited manner (e.g., by only selecting a program or adjusting the pulse amplitude or pulse width), whereas the CP can be used to control all of the stimulation parameters, including which electrodes are cathodes or anodes. In any event, once the IPG is programmed, it is capable providing the required neurostimulation therapy to the patient without being actively linked to the RC or CP.
Of course, rechargeable medical devices, such as IPGs are active devices requiring energy for operation. Oftentimes, it is desirable to recharge an IPG via an external charger, so that a surgical procedure to replace a power depleted IPG can be avoided. To wirelessly convey energy between the external charger and the already implanted IPG, the recharger typically includes an alternating current (AC) charging coil that supplies energy to a similar charging coil located in or on the implantable pulse generator. This system is like a loosely coupled inductive transformer where the primary coil is in the external charger and the secondary coil is in the IPG. The energy received by the charging coil located on the IPG can then be used to directly power the electronic componentry contained within the IPG, or can be stored in a rechargeable battery within the IPG, which can then be used to power the electronic componentry on-demand.
Rechargeble IPGs used for applications that need continuous operation have a need to manage battery status (e.g., the remaining energy capacity of the battery, the remaining time before recharge of the battery is necessary, etc) and to ensure patient compliance with timely recharging of the IPGs. Typically, charge status information is sent from the IPG to an external control device only when the external control device prompts the IPG to do so. For example, oftentimes, the IPG will transmit charge status information to an external control device upon initial communication between these devices. However, because the external control device and IPG will not always be actively linked to each other, the battery capacity of IPG may run dangerously low or otherwise drop to a level insufficient to support continued neurostimulation therapy without ever providing a notification to the patient.
There, thus, remains a need for an improved method and system for notifying a user of the battery status of an rechargeable implantable medical device.